<?php
/**
 * CDbSchema class file.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright 2008-2013 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

/**
 * CDbSchema is the base class for retrieving metadata information.
 *
 * @property CDbConnection $dbConnection Database connection. The connection is active.
 * @property array $tables The metadata for all tables in the database.
 * Each array element is an instance of {@link CDbTableSchema} (or its child class).
 * The array keys are table names.
 * @property array $tableNames All table names in the database.
 * @property CDbCommandBuilder $commandBuilder The SQL command builder for this connection.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @package system.db.schema
 * @since 1.0
 */
abstract class CDbSchema extends CComponent
{
    /**
     * @var array the abstract column types mapped to physical column types.
     * @since 1.1.6
     */
    public $columnTypes = array();

    private $_tableNames = array();
    private $_tables = array();
    private $_connection;
    private $_builder;
    private $_cacheExclude = array();

    /**
     * Loads the metadata for the specified table.
     * @param string $name table name
     * @return CDbTableSchema driver dependent table metadata, null if the table does not exist.
     */
    abstract protected function loadTable($name);

    /**
     * Constructor.
     * @param CDbConnection $conn database connection.
     */
    public function __construct($conn)
    {
        $this->_connection = $conn;
        foreach ($conn->schemaCachingExclude as $name)
            $this->_cacheExclude[$name] = true;
    }

    /**
     * @return CDbConnection database connection. The connection is active.
     */
    public function getDbConnection()
    {
        return $this->_connection;
    }

    /**
     * Obtains the metadata for the named table.
     * @param string $name table name
     * @param boolean $refresh if we need to refresh schema cache for a table.
     * Parameter available since 1.1.9
     * @return CDbTableSchema table metadata. Null if the named table does not exist.
     */
    public function getTable($name, $refresh = false)
    {
        if ($refresh === false && isset($this->_tables[$name]))
            return $this->_tables[$name];
        else {
            if ($this->_connection->tablePrefix !== null && strpos($name, '{{') !== false)
                $realName = preg_replace('/\{\{(.*?)\}\}/', $this->_connection->tablePrefix . '$1', $name);
            else
                $realName = $name;

            // temporarily disable query caching
            if ($this->_connection->queryCachingDuration > 0) {
                $qcDuration = $this->_connection->queryCachingDuration;
                $this->_connection->queryCachingDuration = 0;
            }

            if (!isset($this->_cacheExclude[$name]) && ($duration = $this->_connection->schemaCachingDuration) > 0 && $this->_connection->schemaCacheID !== false && ($cache = Yii::app()->getComponent($this->_connection->schemaCacheID)) !== null) {
                $key = 'yii:dbschema' . $this->_connection->connectionString . ':' . $this->_connection->username . ':' . $name;
                $table = $cache->get($key);
                if ($refresh === true || $table === false) {
                    $table = $this->loadTable($realName);
                    if ($table !== null)
                        $cache->set($key, $table, $duration);
                }
                $this->_tables[$name] = $table;
            } else
                $this->_tables[$name] = $table = $this->loadTable($realName);

            if (isset($qcDuration))  // re-enable query caching
                $this->_connection->queryCachingDuration = $qcDuration;

            return $table;
        }
    }

    /**
     * Returns the metadata for all tables in the database.
     * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
     * @return array the metadata for all tables in the database.
     * Each array element is an instance of {@link CDbTableSchema} (or its child class).
     * The array keys are table names.
     */
    public function getTables($schema = '')
    {
        $tables = array();
        foreach ($this->getTableNames($schema) as $name) {
            if (($table = $this->getTable($name)) !== null)
                $tables[$name] = $table;
        }
        return $tables;
    }

    /**
     * Returns all table names in the database.
     * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
     * If not empty, the returned table names will be prefixed with the schema name.
     * @return array all table names in the database.
     */
    public function getTableNames($schema = '')
    {
        if (!isset($this->_tableNames[$schema]))
            $this->_tableNames[$schema] = $this->findTableNames($schema);
        return $this->_tableNames[$schema];
    }

    /**
     * @return CDbCommandBuilder the SQL command builder for this connection.
     */
    public function getCommandBuilder()
    {
        if ($this->_builder !== null)
            return $this->_builder;
        else
            return $this->_builder = $this->createCommandBuilder();
    }

    /**
     * Refreshes the schema.
     * This method resets the loaded table metadata and command builder
     * so that they can be recreated to reflect the change of schema.
     */
    public function refresh()
    {
        if (($duration = $this->_connection->schemaCachingDuration) > 0 && $this->_connection->schemaCacheID !== false && ($cache = Yii::app()->getComponent($this->_connection->schemaCacheID)) !== null) {
            foreach (array_keys($this->_tables) as $name) {
                if (!isset($this->_cacheExclude[$name])) {
                    $key = 'yii:dbschema' . $this->_connection->connectionString . ':' . $this->_connection->username . ':' . $name;
                    $cache->delete($key);
                }
            }
        }
        $this->_tables = array();
        $this->_tableNames = array();
        $this->_builder = null;
    }

    /**
     * Quotes a table name for use in a query.
     * If the table name contains schema prefix, the prefix will also be properly quoted.
     * @param string $name table name
     * @return string the properly quoted table name
     * @see quoteSimpleTableName
     */
    public function quoteTableName($name)
    {
        if (strpos($name, '.') === false)
            return $this->quoteSimpleTableName($name);
        $parts = explode('.', $name);
        foreach ($parts as $i => $part)
            $parts[$i] = $this->quoteSimpleTableName($part);
        return implode('.', $parts);

    }

    /**
     * Quotes a simple table name for use in a query.
     * A simple table name does not schema prefix.
     * @param string $name table name
     * @return string the properly quoted table name
     * @since 1.1.6
     */
    public function quoteSimpleTableName($name)
    {
        return "'" . $name . "'";
    }

    /**
     * Quotes a column name for use in a query.
     * If the column name contains prefix, the prefix will also be properly quoted.
     * @param string $name column name
     * @return string the properly quoted column name
     * @see quoteSimpleColumnName
     */
    public function quoteColumnName($name)
    {
        if (($pos = strrpos($name, '.')) !== false) {
            $prefix = $this->quoteTableName(substr($name, 0, $pos)) . '.';
            $name = substr($name, $pos + 1);
        } else
            $prefix = '';
        return $prefix . ($name === '*' ? $name : $this->quoteSimpleColumnName($name));
    }

    /**
     * Quotes a simple column name for use in a query.
     * A simple column name does not contain prefix.
     * @param string $name column name
     * @return string the properly quoted column name
     * @since 1.1.6
     */
    public function quoteSimpleColumnName($name)
    {
        return '"' . $name . '"';
    }

    /**
     * Compares two table names.
     * The table names can be either quoted or unquoted. This method
     * will consider both cases.
     * @param string $name1 table name 1
     * @param string $name2 table name 2
     * @return boolean whether the two table names refer to the same table.
     */
    public function compareTableNames($name1, $name2)
    {
        $name1 = str_replace(array('"', '`', "'"), '', $name1);
        $name2 = str_replace(array('"', '`', "'"), '', $name2);
        if (($pos = strrpos($name1, '.')) !== false)
            $name1 = substr($name1, $pos + 1);
        if (($pos = strrpos($name2, '.')) !== false)
            $name2 = substr($name2, $pos + 1);
        if ($this->_connection->tablePrefix !== null) {
            if (strpos($name1, '{') !== false)
                $name1 = $this->_connection->tablePrefix . str_replace(array('{', '}'), '', $name1);
            if (strpos($name2, '{') !== false)
                $name2 = $this->_connection->tablePrefix . str_replace(array('{', '}'), '', $name2);
        }
        return $name1 === $name2;
    }

    /**
     * Resets the sequence value of a table's primary key.
     * The sequence will be reset such that the primary key of the next new row inserted
     * will have the specified value or max value of a primary key plus one (i.e. sequence trimming).
     * @param CDbTableSchema $table the table schema whose primary key sequence will be reset
     * @param integer|null $value the value for the primary key of the next new row inserted.
     * If this is not set, the next new row's primary key will have the max value of a primary
     * key plus one (i.e. sequence trimming).
     * @since 1.1
     */
    public function resetSequence($table, $value = null)
    {
    }

    /**
     * Enables or disables integrity check.
     * @param boolean $check whether to turn on or off the integrity check.
     * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
     * @since 1.1
     */
    public function checkIntegrity($check = true, $schema = '')
    {
    }

    /**
     * Creates a command builder for the database.
     * This method may be overridden by child classes to create a DBMS-specific command builder.
     * @return CDbCommandBuilder command builder instance
     */
    protected function createCommandBuilder()
    {
        return new CDbCommandBuilder($this);
    }

    /**
     * Returns all table names in the database.
     * This method should be overridden by child classes in order to support this feature
     * because the default implementation simply throws an exception.
     * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
     * If not empty, the returned table names will be prefixed with the schema name.
     * @throws CDbException if current schema does not support fetching all table names
     * @return array all table names in the database.
     */
    protected function findTableNames($schema = '')
    {
        throw new CDbException(Yii::t('yii', '{class} does not support fetching all table names.',
            array('{class}' => get_class($this))));
    }

    /**
     * Converts an abstract column type into a physical column type.
     * The conversion is done using the type map specified in {@link columnTypes}.
     * These abstract column types are supported (using MySQL as example to explain the corresponding
     * physical types):
     * <ul>
     * <li>pk: an auto-incremental primary key type, will be converted into "int(11) NOT NULL AUTO_INCREMENT PRIMARY KEY"</li>
     * <li>string: string type, will be converted into "varchar(255)"</li>
     * <li>text: a long string type, will be converted into "text"</li>
     * <li>integer: integer type, will be converted into "int(11)"</li>
     * <li>boolean: boolean type, will be converted into "tinyint(1)"</li>
     * <li>float: float number type, will be converted into "float"</li>
     * <li>decimal: decimal number type, will be converted into "decimal"</li>
     * <li>datetime: datetime type, will be converted into "datetime"</li>
     * <li>timestamp: timestamp type, will be converted into "timestamp"</li>
     * <li>time: time type, will be converted into "time"</li>
     * <li>date: date type, will be converted into "date"</li>
     * <li>binary: binary data type, will be converted into "blob"</li>
     * </ul>
     *
     * If the abstract type contains two or more parts separated by spaces (e.g. "string NOT NULL"), then only
     * the first part will be converted, and the rest of the parts will be appended to the conversion result.
     * For example, 'string NOT NULL' is converted to 'varchar(255) NOT NULL'.
     * @param string $type abstract column type
     * @return string physical column type.
     * @since 1.1.6
     */
    public function getColumnType($type)
    {
        if (isset($this->columnTypes[$type]))
            return $this->columnTypes[$type];
        elseif (($pos = strpos($type, ' ')) !== false) {
            $t = substr($type, 0, $pos);
            return (isset($this->columnTypes[$t]) ? $this->columnTypes[$t] : $t) . substr($type, $pos);
        } else
            return $type;
    }

    /**
     * Builds a SQL statement for creating a new DB table.
     *
     * The columns in the new  table should be specified as name-definition pairs (e.g. 'name'=>'string'),
     * where name stands for a column name which will be properly quoted by the method, and definition
     * stands for the column type which can contain an abstract DB type.
     * The {@link getColumnType} method will be invoked to convert any abstract type into a physical one.
     *
     * If a column is specified with definition only (e.g. 'PRIMARY KEY (name, type)'), it will be directly
     * inserted into the generated SQL.
     *
     * @param string $table the name of the table to be created. The name will be properly quoted by the method.
     * @param array $columns the columns (name=>definition) in the new table.
     * @param string $options additional SQL fragment that will be appended to the generated SQL.
     * @return string the SQL statement for creating a new DB table.
     * @since 1.1.6
     */
    public function createTable($table, $columns, $options = null)
    {
        $cols = array();
        foreach ($columns as $name => $type) {
            if (is_string($name))
                $cols[] = "\t" . $this->quoteColumnName($name) . ' ' . $this->getColumnType($type);
            else
                $cols[] = "\t" . $type;
        }
        $sql = "CREATE TABLE " . $this->quoteTableName($table) . " (\n" . implode(",\n", $cols) . "\n)";
        return $options === null ? $sql : $sql . ' ' . $options;
    }

    /**
     * Builds a SQL statement for renaming a DB table.
     * @param string $table the table to be renamed. The name will be properly quoted by the method.
     * @param string $newName the new table name. The name will be properly quoted by the method.
     * @return string the SQL statement for renaming a DB table.
     * @since 1.1.6
     */
    public function renameTable($table, $newName)
    {
        return 'RENAME TABLE ' . $this->quoteTableName($table) . ' TO ' . $this->quoteTableName($newName);
    }

    /**
     * Builds a SQL statement for dropping a DB table.
     * @param string $table the table to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping a DB table.
     * @since 1.1.6
     */
    public function dropTable($table)
    {
        return "DROP TABLE " . $this->quoteTableName($table);
    }

    /**
     * Builds a SQL statement for truncating a DB table.
     * @param string $table the table to be truncated. The name will be properly quoted by the method.
     * @return string the SQL statement for truncating a DB table.
     * @since 1.1.6
     */
    public function truncateTable($table)
    {
        return "TRUNCATE TABLE " . $this->quoteTableName($table);
    }

    /**
     * Builds a SQL statement for adding a new DB column.
     * @param string $table the table that the new column will be added to. The table name will be properly quoted by the method.
     * @param string $column the name of the new column. The name will be properly quoted by the method.
     * @param string $type the column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
     * into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
     * For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
     * @return string the SQL statement for adding a new column.
     * @since 1.1.6
     */
    public function addColumn($table, $column, $type)
    {
        return 'ALTER TABLE ' . $this->quoteTableName($table)
        . ' ADD ' . $this->quoteColumnName($column) . ' '
        . $this->getColumnType($type);
    }

    /**
     * Builds a SQL statement for dropping a DB column.
     * @param string $table the table whose column is to be dropped. The name will be properly quoted by the method.
     * @param string $column the name of the column to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping a DB column.
     * @since 1.1.6
     */
    public function dropColumn($table, $column)
    {
        return "ALTER TABLE " . $this->quoteTableName($table)
        . " DROP COLUMN " . $this->quoteColumnName($column);
    }

    /**
     * Builds a SQL statement for renaming a column.
     * @param string $table the table whose column is to be renamed. The name will be properly quoted by the method.
     * @param string $name the old name of the column. The name will be properly quoted by the method.
     * @param string $newName the new name of the column. The name will be properly quoted by the method.
     * @return string the SQL statement for renaming a DB column.
     * @since 1.1.6
     */
    public function renameColumn($table, $name, $newName)
    {
        return "ALTER TABLE " . $this->quoteTableName($table)
        . " RENAME COLUMN " . $this->quoteColumnName($name)
        . " TO " . $this->quoteColumnName($newName);
    }

    /**
     * Builds a SQL statement for changing the definition of a column.
     * @param string $table the table whose column is to be changed. The table name will be properly quoted by the method.
     * @param string $column the name of the column to be changed. The name will be properly quoted by the method.
     * @param string $type the new column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
     * into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
     * For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
     * @return string the SQL statement for changing the definition of a column.
     * @since 1.1.6
     */
    public function alterColumn($table, $column, $type)
    {
        return 'ALTER TABLE ' . $this->quoteTableName($table) . ' CHANGE '
        . $this->quoteColumnName($column) . ' '
        . $this->quoteColumnName($column) . ' '
        . $this->getColumnType($type);
    }

    /**
     * Builds a SQL statement for adding a foreign key constraint to an existing table.
     * The method will properly quote the table and column names.
     * @param string $name the name of the foreign key constraint.
     * @param string $table the table that the foreign key constraint will be added to.
     * @param string $columns the name of the column to that the constraint will be added on. If there are multiple columns, separate them with commas.
     * @param string $refTable the table that the foreign key references to.
     * @param string $refColumns the name of the column that the foreign key references to. If there are multiple columns, separate them with commas.
     * @param string $delete the ON DELETE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
     * @param string $update the ON UPDATE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
     * @return string the SQL statement for adding a foreign key constraint to an existing table.
     * @since 1.1.6
     */
    public function addForeignKey($name, $table, $columns, $refTable, $refColumns, $delete = null, $update = null)
    {
        $columns = preg_split('/\s*,\s*/', $columns, -1, PREG_SPLIT_NO_EMPTY);
        foreach ($columns as $i => $col)
            $columns[$i] = $this->quoteColumnName($col);
        $refColumns = preg_split('/\s*,\s*/', $refColumns, -1, PREG_SPLIT_NO_EMPTY);
        foreach ($refColumns as $i => $col)
            $refColumns[$i] = $this->quoteColumnName($col);
        $sql = 'ALTER TABLE ' . $this->quoteTableName($table)
            . ' ADD CONSTRAINT ' . $this->quoteColumnName($name)
            . ' FOREIGN KEY (' . implode(', ', $columns) . ')'
            . ' REFERENCES ' . $this->quoteTableName($refTable)
            . ' (' . implode(', ', $refColumns) . ')';
        if ($delete !== null)
            $sql .= ' ON DELETE ' . $delete;
        if ($update !== null)
            $sql .= ' ON UPDATE ' . $update;
        return $sql;
    }

    /**
     * Builds a SQL statement for dropping a foreign key constraint.
     * @param string $name the name of the foreign key constraint to be dropped. The name will be properly quoted by the method.
     * @param string $table the table whose foreign is to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping a foreign key constraint.
     * @since 1.1.6
     */
    public function dropForeignKey($name, $table)
    {
        return 'ALTER TABLE ' . $this->quoteTableName($table)
        . ' DROP CONSTRAINT ' . $this->quoteColumnName($name);
    }

    /**
     * Builds a SQL statement for creating a new index.
     * @param string $name the name of the index. The name will be properly quoted by the method.
     * @param string $table the table that the new index will be created for. The table name will be properly quoted by the method.
     * @param string $column the column(s) that should be included in the index. If there are multiple columns, please separate them
     * by commas. Each column name will be properly quoted by the method, unless a parenthesis is found in the name.
     * @param boolean $unique whether to add UNIQUE constraint on the created index.
     * @return string the SQL statement for creating a new index.
     * @since 1.1.6
     */
    public function createIndex($name, $table, $column, $unique = false)
    {
        $cols = array();
        $columns = preg_split('/\s*,\s*/', $column, -1, PREG_SPLIT_NO_EMPTY);
        foreach ($columns as $col) {
            if (strpos($col, '(') !== false)
                $cols[] = $col;
            else
                $cols[] = $this->quoteColumnName($col);
        }
        return ($unique ? 'CREATE UNIQUE INDEX ' : 'CREATE INDEX ')
        . $this->quoteTableName($name) . ' ON '
        . $this->quoteTableName($table) . ' (' . implode(', ', $cols) . ')';
    }

    /**
     * Builds a SQL statement for dropping an index.
     * @param string $name the name of the index to be dropped. The name will be properly quoted by the method.
     * @param string $table the table whose index is to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping an index.
     * @since 1.1.6
     */
    public function dropIndex($name, $table)
    {
        return 'DROP INDEX ' . $this->quoteTableName($name) . ' ON ' . $this->quoteTableName($table);
    }

    /**
     * Builds a SQL statement for adding a primary key constraint to an existing table.
     * @param string $name the name of the primary key constraint.
     * @param string $table the table that the primary key constraint will be added to.
     * @param string|array $columns comma separated string or array of columns that the primary key will consist of.
     * Array value can be passed since 1.1.14.
     * @return string the SQL statement for adding a primary key constraint to an existing table.
     * @since 1.1.13
     */
    public function addPrimaryKey($name, $table, $columns)
    {
        if (is_string($columns))
            $columns = preg_split('/\s*,\s*/', $columns, -1, PREG_SPLIT_NO_EMPTY);
        foreach ($columns as $i => $col)
            $columns[$i] = $this->quoteColumnName($col);
        return 'ALTER TABLE ' . $this->quoteTableName($table) . ' ADD CONSTRAINT '
        . $this->quoteColumnName($name) . '  PRIMARY KEY ('
        . implode(', ', $columns) . ' )';
    }

    /**
     * Builds a SQL statement for removing a primary key constraint to an existing table.
     * @param string $name the name of the primary key constraint to be removed.
     * @param string $table the table that the primary key constraint will be removed from.
     * @return string the SQL statement for removing a primary key constraint from an existing table.
     * @since 1.1.13
     */
    public function dropPrimaryKey($name, $table)
    {
        return 'ALTER TABLE ' . $this->quoteTableName($table) . ' DROP CONSTRAINT '
        . $this->quoteColumnName($name);
    }
}
